Pipe support system with multiple clamps

ABSTRACT

The present invention relates to an apparatus for and a method of holding high top tension pipeline (101) during pipe-lay from a rolling and pitching vessel (730). In one implementation, a clamp system (711, 712) for supporting a pipe on a vessel includes a first clamp for coupling to the pipe and a second clamp for coupling to the pipe. The second clamp is disposed above the first clamp. At least one of the first clamp or the second clamp is movable relative to the other of the first clamp or the second clamp.

BACKGROUND Field

Aspects of the present disclosure generally relate to apparatus for andmethods of holding high top tension pipeline during pipe-lay from arolling and pitching vessel.

Description of the Related Art

There are many methods of laying deep water pipelines, such as reel-lay,J-Lay, and the like. When using these methods, at some point pipe isheld in either a collar support or a pipe clamp, to install and weldadditional lengths of pipe, or to install inline and second-endfittings.

Pipelines laid in deep water depths are subjected to high axial load dueto the pipeline self-weight, and this in turn creates high axialstresses in the pipe wall. Sometimes, axial stresses alone reach 60-80%of material yield stress. Axial stresses which are acceptable forinstallation are set by design codes.

All vessels roll and pitch as a result of wave action. When laying apipeline from a vessel, the pipeline is often held rigidly in a pipeclamp (approaching an “Encastre” support condition). The pipe at thebase of the clamp will be subjected not only to the high axial stress,but also high bending stresses as a result of vessel roll and pitchmotions. FIG. 1 illustrates a conventional single friction clamp 100having a pipe 101 suspended therefrom. Arrows 102 and 103 illustrateshow axial and bending stresses, respectively, in the pipe 101.

The total stress in the pipe is the summation of the axial and bendingstresses, which is applied to the pipe 101 each time the vessel rolls orpitches, resulting in cyclical stressing. The magnitude of the bendingstress is a product of the roll or pitch angle and the axial loadapplied. Cyclic bending stress can result in fatigue damage to the pipe101 in the area directly below the clamp 100, which is the area of pipe101 subjected to high combined axial/bending stresses.

FIG. 2A illustrates axial and bending stress distribution along one sideof an axial length of a section of the pipe 101 below the conventionalsingle friction clamp 100 of FIG. 1. FIG. 2B illustrates axial andbending stress distribution along another side of the axial length ofthe section of the pipe 101 below the conventional single friction clamp101 of FIG. 1. FIGS. 2A and 2B illustrate stress distribution alongopposite sides of a section of the pipe 101 below the conventionalsingle friction clamp 100 of FIG. 1, in which FIG. 2A shows one side ofthe pipe being (at least partially) compressed from the bending stressand FIG. 2B shows the other side of the pipe being tensioned from thebending stress. Thus, FIG. 2A shows a resultant stress 203A from apositive axial stress 201A (tensioning the pipe) and a negative bendingstress 202A (compressing the pipe), in which the resultant stress 203Aon the pipe is shown as overall positive and tensioning the pipe. FIG.2B shows a resultant stress 203B from a positive axial stress 201B(tensioning the pipe) and a positive bending stress 202B (alsotensioning the pipe), in which the resultant stress 203B on the pipe isshown as overall positive and tensioning the pipe. The resultant stress203B for the side of the pipe in FIG. 2B is generally larger than theresultant stress 203A for the side of the pipe in FIG. 2A. As a vesselpitches and rolls from side-to-side, each side of the pipe may cyclebetween the stress distribution shown in FIG. 2A to the stressdistribution shown in FIG. 2B, and vice-versa. FIGS. 2A and 2B also donot show stress that may be applied to the axial length of the sectionof the pipe 101 from heave of a vessel (e.g., up-and-down movement ofthe vessel), which may vary the axial stress distributed to the pipe.FIGS. 2A and 2B focus on the roll and pitch of the vessel.

Conventionally, to reduce the fatigue damage to the pipe 101, theclamping time is shortened. The J-Lay technique, where the pipeline islaid by welding successive sections of pipe together, is particularlysensitive to the time that the pipe 101 can be held in the clamp 100before exceeding fatigue limits. To provide sufficient time for weldingoperations, more stable (e.g., larger) vessels are often utilized, thusincreasing day rates and project costs for pipe installation.

Therefore, what is needed is an improved apparatus for and method ofholding high top tension pipeline during pipe-lay from a rolling andpitching vessel.

SUMMARY

Aspects of the present disclosure generally relate to apparatus for andmethods of holding high top tension pipeline during pipe-lay from arolling and pitching vessel.

In one implementation, a clamp system for supporting a pipe on a vesselincludes a first clamp for coupling to the pipe and a second clamp forcoupling to the pipe. The second clamp is disposed above the firstclamp. At least one of the first clamp or the second clamp is movablerelative to the other of the first clamp or the second clamp.

In one implementation, a method of supporting a pipe on a vesselincludes coupling a first clamp to a pipe. The pipe includes alongitudinal axis. The method includes coupling a second clamp to thepipe. The method also includes moving at least one of the first clamp orthe second clamp relative to the other of the first clamp or the secondclamp while the first clamp and the second clamp are clamped to thepipe.

In one implementation, a clamp includes a plurality of clamping layerscomprising one or more lower layers and one or more upper layersdisposed above the one or more lower layers. Each of the one or morelower layers includes one or more variable squeeze cylinders, and one ormore actuating clamp members. A pressure within each of the one or morevariable squeeze cylinders is maintained at a constant value when theone or more actuating clamp members are in contact with a pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofscope, as the disclosure may admit to other equally effectiveembodiments.

FIG. 1 illustrates a conventional single friction clamp having a pipesuspended therefrom.

FIG. 2A illustrates axial and bending stress distribution along one sideof an axial length of a section of a pipe below the conventional singlefriction clamp of FIG. 1.

FIG. 2B illustrates axial and bending stress distribution along anotherside of the axial length of the section of the pipe below theconventional single friction clamp of FIG. 1.

FIG. 3 illustrates a dual clamp arrangement in a retracted state,according to one aspect of the disclosure.

FIGS. 4A and 4B illustrate the dual clamp arrangement of FIG. 3 in anextended position, according to one aspect of the disclosure.

FIG. 5A illustrates a single clamp and a pipe, along with a chart ofstress distribution of the pipe below the single clamp.

FIG. 5B illustrates a dual clamp arrangement without induced axialcompression, according to one aspect of the disclosure.

FIG. 5C illustrates a dual clamp arrangement with induced axialcompression, according to one aspect of the disclosure.

FIG. 6 illustrates a clamp, according to one aspect of the disclosure.

FIGS. 7A-7E illustrate a clamp system, according to one aspect of thedisclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

FIG. 3 illustrates a clamp system or dual clamp arrangement 210 in aretracted state, according to one aspect of the disclosure. The dualclamp arrangement 210 employs two clamps including a first clamp 211 anda second clamp 212. First clamp 211 is a lower clamp (or collar),holding some or all of the axial load of the pipe 101, with no momentresistance. First clamp 211 may be, for example, a swinging friction orcollar clamp that restricts axial movement of the pipe 101 but allowsthe pipe 101 to swing. Second clamp 212 is an upper clamp which securesan upper end of the pipe 101 above the first clamp 211, and restrainsbending moments to allow welding or other operations to be performed atthe upper end of the pipe 101. The second clamp 212 may be a friction orcollar clamp that is rigidly supported and restricts swinging of thepipe 101. Using dual clamps 211 and 212, high axial stress is removedsome distance below the second clamp 212 (e.g., the moment restrainingclamp), by the lower first clamp 211 located where the bending momentand bending stresses are low. The separation of functions for the clamps211, 212 (e.g., moment restraint for second clamp 212 and axialrestraint for first clamp 211) reduces fatigue and damage to the pipe101. Thus, small (and less costly) vessels can be utilized to performdeep water pipe-lay.

The second clamp 212 is an upper clamp and the first clamp 211 is alower clamp. The second clamp 212 and the first clamp 211 areoperatively coupled through actuators 213. Each actuator of theactuators 213 includes a cylinder, such as a hydraulic cylinder or apneumatic cylinder. The actuators 213 are coupled to a base 220 of thesecond clamp 212, and to a support 221 of the first clamp 211. Tofacilitate relative movement between the actuators 213 and the clamps211, 212, the actuators 213 are coupled to the support 221 at a firstend and the base 220 at a second end through moveable connections 222.The moveable connections 222 may be pivoting connections, asillustrated, or types of connections such as spherical bearings (forexample ball bearings) or ball-in-socket joints to provide increasedrange of motion. In one example, the moveable connections 222 at theupper end of the actuators 213 pivot at 90 degrees relative to themoveable connections 222 at the lower end of the actuators 213. Whileaspects of the present disclosure are described with respect tohydraulic cylinders of the actuators 213, other actuating or extendingconnection members are also contemplated, and need not necessarily becylindrically-shaped.

The first clamp 211 is movable relative to the second clamp 212 and/orthe second clamp 212 is movable relative to the first clamp 211. Thepresent disclosure contemplates that moving one of the first or secondclamps 211, 212 relative to the other of the first or second clamps mayinclude moving the other of the first or second clamps 211, 212. Forexample, the present disclosure contemplates that moving the secondclamp 212 relative to the first clamp 211 may include actuating theactuators 213 to move the first clamp 211 while the second clamp 212remains stationary.

FIGS. 4A and 4B illustrate the dual clamp arrangement of FIG. 3 in anextended position, according to one aspect of the disclosure. The secondclamp 212 and first clamp 211 are actuatable using the actuators 213between the extended position illustrated in FIGS. 4A and 4B and theretracted position illustrated in FIG. 3. When laying larger diameterpipes, high bending moments may extend a significant distance below thesecond clamp 212. In such a case, the first clamp 211 can be loweredaxially along the pipe 101 to a depth where the bending moments arewithin acceptable limits, and then secured on the pipe 101. In oneexample, a plurality of the actuators 213 (four are shown), having forexample hydraulic or pneumatic cylinders, may facilitate actuationbetween the clamps 211 and 212. To facilitate movement of the firstclamp 211 relative to the pipe 101, the first clamp 211 may include aplurality of rollers 225 at upper and/or lower ends thereof to engagethe pipe 101. After clamping both the first clamp 211 and second clamp212 to the pipe 101, the actuating cylinders 213 supporting the firstclamp 211 are tensioned, taking part or all of the catenary top tension.

In the examples of FIGS. 4A and 4B, the first clamp 211 of the dualclamp arrangement 210 is fully extended and holding an axial load of thepipe 101 with no moment restraint, while the second clamp 212 restrainsonly bending moment. The first clamp 211 is suspended on the actuators213, and annulus pressure can be set to support a specific load whilepressure is held constant on hydraulic accumulators.

In one embodiment, which can be combined with other embodiments, it iscontemplated that a proportion of pipe top tension that is supported bythe first clamp 211 is adjustable from zero upward to a desired value.In doing so, it is contemplated that the pipe 101 between the clamps211, 212 may be put into compression. By using such compression, theaxial stress in the pipe 101 between the clamps 211, 212 iscontrollable. The axial stress between the clamps 211, 212 iscontrollable for example using the actuators 213, such as by alteringthe magnitude and/or direction of force applied between the base 201 andthe support 221 by one or more of the actuators 213. In one example, oneor more of the actuators 213 are at least partially retracted to axiallyapply compressive stress to the pipe 101 between the clamps 211, 212. Inone example, an actuating force applied to actuate one or more of theactuators 213 is reduced to axially apply compressive stress to the pipe101 between the clamps 211, 212. One or more of the actuators 213 maypull upwardly on the first clamp 211 to axially apply compressive stressto the pipe 101 between the clamps 211, 212. In one example, thecompressive stress can be applied so that the compressive stress isgreater than the bending stress caused by the moment, thus resulting inlittle to no tensile bending stresses in the pipe 101.

Thus, the disclosed dual clamp arrangement 210 facilitates reducing orcompletely eliminating fatigue damage of the pipe 101 at least in partby mitigating tensile bending stresses induced thereto. This isillustrated by the axial and bending stress distribution in the pipe 101between the second clamp 212 and the first clamp 211, as shown in FIG. 5below. However, the present disclosure is not so limited, as the lowerfirst clamp 211 may not be tensioned with respect to the upper secondclamp 212 such that the first clamp 211 does not induce compression intothe pipe 101 between the clamps 211, 212. For example, after the lowerclamp 211 has been moved to a desired position with respect to thesecond clamp 212, the actuators 213 or cylinders of the actuators 213may be locked (e.g., hydraulically locked) such that the actuators 213act similar to a fixed link. If used as a fixed link, the actuators 213may prevent fluctuating axial stresses (e.g., from heave of the vessel)being translated through the first clamp 211 and to the pipe 101 betweenthe clamps 211, 212.

The present disclosure contemplates that linkage may be used in place ofthe actuators 213. For example, a link having a spherical bearing ateach end thereof may be used in place of each actuator 213 to facilitatecost reduction.

The present disclosure also contemplates that the actuators describedthroughout, such as actuators 213, may be fully extended and locked intoplace to function as rigid links.

FIGS. 5A-5C illustrate stress distribution according to different clampconfigurations. FIG. 5A illustrates a single clamp 501 and a pipe 503,along with a chart 504 of stress distribution of the pipe 503 below thesingle clamp 501. In FIG. 5A, an axial stress 505 and a bending stress507 combine as an overall stress 509. FIG. 5B illustrates a dual clamparrangement without induced axial compression, according to one aspectof the disclosure. The dual clamp arrangement includes a first clamp511, a second clamp 513 above the first clamp 511. The first clamp 511and the second clamp 513 clamp to a pipe 515. FIG. 5B also illustrates achart 516 of stress distribution of the pipe 515 below the second clamp513. In FIG. 5B, an axial stress 517 and a bending stress 519 combine asan overall stress 521. In the dual clamp arrangement of FIG. 5B, thedual clamp arrangement is completely axially supported by the firstclamp 511.

FIG. 5C illustrates a dual clamp arrangement with induced axialcompression, according to one aspect of the disclosure. The dual clamparrangement includes a first clamp 529 and a second clamp 531 above thefirst clamp 529. The first clamp 529 and the second clamp 531 clamp to apipe 533. FIG. 5C also illustrates a chart 535 of stress distribution ofthe pipe 533 below the second clamp 531. In FIG. 5C, an axial stress 523and a bending stress 525 combine as an overall stress 527. Compressivestress is applied axially to a section of the pipe 515 between the firstclamp 529 and the second clamp 531. The first clamp 529 is used to applycompressive stress to the section of the pipe 515.

As illustrated in the dual clamp arrangement of FIG. 5C in which axialcompression is induced between the clamps 529, 531, bending stress isgreatly reduced. In the dual clamp arrangement of FIG. 5C, the overallstress 527 of the pipe 533 is reduced in the section between the firstclamp 529 and the second clamp 531, as compared to the overall stress521 at the same location in FIG. 5B and the overall stress 509 at thesame location in FIG. 5A.

FIG. 6 illustrates a clamp 611, according to one aspect of thedisclosure. The clamp 611 may be used as one or both of clamps 211 or212.

Conventional friction grip clamps include of a number of layers, eachsupporting a portion of the top tension load. These layers restrain thepipe axial load and bending moment, providing a very stiff “encastre”support for the pipe. Although conventional friction grip clamps cansupport pipes, such support results in high pipe stresses as acombination of axial and bending stresses at the base of the clamp(together with high shear stresses), as discussed above.

In contrast, the clamp 611 utilizes one or more upper layers 620 a-620 d(four are shown) to provide axial and bending moment support, and one ormore lowers layers 621 a-621 c (three are shown) as a variable stiffnessspring. Variability in the spring stiffness of the lower layers 621a-621 c is achieved by controlling a hydraulic pressure in variable“squeeze” cylinders (such as the cylinders 636 described below). Thehydraulic pressure can be maintained at a constant value by accumulators622 (six are shown). Such a support regime leads to more compliant lowerlayers 621 a-621 c of the clamp 611, and thus “softens” the support tothe pipe 101 at the base of the clamp 611. This in turn reduces thebending stresses induced in the pipe 101. Each of the accumulators 622may include a gas side separated from a hydraulic liquid side tofacilitate maintaining a certain pressure. The accumulators 622 mayfunction as gas springs.

The clamp 611 is shown with four upper layers 620 a-620 d and threelower layers 621 a-6212 c, however, it is contemplated that the clamp611 can be extended or retracted with sufficient numbers of upper and/orlower layers to provide the desired support stiffness.

Each layer 620 of the clamp 611 includes a housing 630, one or moreactuating clamp members 631 disposed in the housing 630, and an inlet632 at a radially outward end of the housing 630 for receiving a signalor fluid for actuating the actuating clamp member 631 into engagementwith the pipe 101. In one example, fluid enters a cylinder 636 for eachactuating clamp member 631 through the inlet 632. Each layer 621 a-621 cis similarly constructed, but additionally includes a respectiveaccumulator 622 per actuating clamp member 631, and a correspondingpressure gauge 634 per accumulator 622 (one is labeled).

In one example, each housing 630 is a cylindrical member configured tohouse a plurality of actuating clamp members 631 radially therearound.In one example, each housing 630 is a discrete member, configured tohouse an individual actuating clamp member 631. The actuating clampmembers may be disposed at a predetermined angular distance from oneanother around the pipe 101, such as 180 degrees, 120 degrees, or 90degrees.

The present disclosure contemplates that the clamp 611 may be used in asingle clamp configuration rather than a dual clamp configuration. Insuch examples, due to the variability in the spring stiffness of thelower layers 621 a-621 c, the clamp 611 provides adequate mitigation ofbending stresses without the need for a second clamp.

FIGS. 7A-7E illustrate a clamp system 710, according to one aspect ofthe disclosure. The clamp system 710 includes a lower clamp 711 and anupper clamp 712 for supporting the pipe 101. As with the aboveembodiments, the lower clamp 711 may be a swinging friction or collarclamp that restricts axial movement of the pipe 101 but allows the pipe101 to swing. Further, the upper clamp 712 secures to the pipe 101 abovethe lower clamp 711 and restrains bending moments to allow welding orother operations to be performed at the upper end of the pipe 101. Theupper clamp 712 may be a friction or collar clamp that is rigidlysupported and restricts swinging of the pipe 101.

The clamp system 710 as shown includes a hull 730 and an overheadstructure 732, such as a tower, coupled to and supported by the hull730. The overhead structure 732 is shown as rotatably coupled to thehull 730 through pins 734. The lower clamp 711 and the upper clamp 712are supported by and coupled to the overhead structure 732, such as byeach being separately supported and coupled to the overhead structure732.

The upper clamp 712 is translatably coupled to the overhead structure732, such as through actuators or sheaves 736. As shown, the sheaves 736are coupled to the upper clamp 712, and winches or pulleys may use linesor tensioners with the sheaves 736 to translate and move the upper clamp712 with respect to the overhead structure 732. The lines or tensionersmay be attached to the sheaves 736 at a first end and the overheadstructure 732 at a second end. The lower clamp 711 is rotatably coupledto the overhead structure 732, such as through moveable connections orspherical bearings 738 (e.g., ball bearings). Links 740 are used tocouple the lower clamp 711 to the overhead structure 732, and sphericalbearings 738 may be used at one or both ends of the links 740 torotatably couple the lower clamp 711 to the overhead structure 732.

As with the aspects illustrated in FIGS. 3, 4A, and 4B, the lower clamp711 and the upper clamp 712 are movable with respect to each other, suchas when each of the clamps 711, 712 are supporting the pipe 101, or whenonly one of the clamps 711, 712 is supporting the pipe 101. For example,the clamps 711, 712 are movable along a longitudinal axis 190 of thepipe 101 with respect to each other, such as to adjust a distance 750between the upper clamp 712 and the lower clamp 711. In the aspectsillustrated in FIGS. 7A-7E, the upper clamp 712 and the lower clamp 711are movable along the longitudinal axis 190 of the pipe 101 with respectto each other by moving the upper clamp 712 relative to the overheadstructure 732, such as through the sheaves 736.

The upper clamp 712 and the lower clamp 711 are also movable along thelongitudinal axis 190 of the pipe 101 with respect to each other byactuating one or more actuators of each link 740 to move the lower clamp711 relative to the overhead structure 732. Each of one or moreactuators includes a hydraulic cylinder and/or a pneumatic cylinder, andis connected to an accumulator that supplies pressurized fluid to thehydraulic or pneumatic cylinder. In one example the one or moreactuators are used as the links 740, and are coupled at a first end tothe lower clamp 711 through the spherical bearings 738 and at a secondend to the overhead structure 732. In one example the one or moreactuators are actuators 790 that are disposed between each link 740 andthe overhead structure 732, as illustrated in FIGS. 7A, 7C, and 7D. Eachof the actuators 790 is coupled to one of the links 740 through aspherical bearing 738 at a first end and to the overhead structure 732through a spherical bearing 738 at a second end.

The one or more actuators of the links 740 facilitate positioning of thelower clamp 711 while heave of the vessel changes. In one example, pipe101 is layed at an angle relative to the hull 730 and/or a gravitationalforce 799. In such an example, the overhead structure 732 is disposed atan angle relative to the hull 730 and/or the gravitational force 799 byrotating the overhead structure 732 about the pins 734. In such anexample, the actuators of the links 740 can facilitate maintaining theclamp 711 (such as a housing of the clamp 711) at a gap from the pipe101 during heave changes of the vessel, while welding or otheroperations are performed at the upper end of the pipe 101. In oneembodiment, which can be combined with other embodiments, the actuators790 are disposed in a horizontal fashion when the overhead structure 732is disposed vertically and is parallel to the gravitational force 799.

In one embodiment, which can be combined with other embodiments, thelongitudinal axis 190 extends along a geometric center of the pipe 101.

Further, the lower and upper clamps 711, 712 are rotatable with respectto each other in one or more planes that are parallel to thelongitudinal axis 190 of the pipe 101. For example, the upper clamp 712and the lower clamp 711 are able to rotate with respect to each other intwo planes simultaneously that are parallel to the longitudinal axis ofthe pipe 101. The lower clamp 711 is able to swing in one or moredirections with respect to the upper clamp 712 through the links 740 andthe spherical bearings 738. Furthermore, each of the clamps 711, 712 maybe used for separate functions (e.g., moment restraint for upper clamp712 and axial restraint for lower clamp 711) to reduce fatigue anddamage to the pipe 101.

FIG. 7A illustrates an X-axis, a Y-axis, and a Z-axis of the overheadstructure 732 that define an X-Y plane, an X-Z plane, and a Y-Z plane.The lower and upper clamps 711, 712 are rotatable with respect to eachother in two planes (e.g., the X-Z plane and the Y-Z plane) that areparallel to the longitudinal axis 190. The lower and upper clamps 711,712 are also rotatable with respect to each other in a plane (e.g., theX-Y plane) that is perpendicular to the longitudinal axis 190.

In one or more embodiments, one or more different components orstructures may be used to substitute for, or used in addition to, thefunctionality of the links 740 and the spherical bearings 738. Forexample, a gimbal or other support structure may be coupled between thelower clamp 711 and the hull 730 or the overhead structure 732 to enablethe upper clamp 712 and the lower clamp 711 to rotate with respect toeach other in two planes simultaneously that are parallel to thelongitudinal axis 190 of the pipe 101. The gimbal or support structuremay include one or more elastomeric or biasing supports positionedbetween plates, or layered with plates, with the lower clamp 711supported by the gimbal or support structure. Thus, the lower clamp 711may be able to rotate with respect to the upper clamp 712 through thegimbal or support structure.

Referring still to FIGS. 7A-7E, the clamp system 710 includes a platform742 that enables access to the pipe 101. The upper clamp 712 ispositioned below and coupled to the platform 742. The upper clamp 712and/or the lower clamp 711 are also movable with respect to the platform742. The lower clamp 711 is movable with respect to the platform 742along the longitudinal axis 190 of the pipe 101, such as through thesheaves 736. Further, the upper clamp 712 is movable with respect to theplatform 742 by being rotatable in one or more planes parallel to thelongitudinal axis 190 of the pipe 101. For example, actuators 744 arecoupled between the platform 742 and the upper clamp 712 to actuate andenable movement, as desired, between the platform 742 and the upperclamp 712. Each of the actuators 744 may include hydraulic cylindersand/or pneumatic cylinders. In an event that the vessel, and thereforethe hull 730 and the overhead structure 732 are not level, the platform742 may be rotated with respect to the upper clamp 712 to provide a morelevel environment for workers on the platform 742 that are accessing thepipe 101.

The pipe 101 of the clamp system 710 illustrated in FIGS. 7A-7E mayundergo fluctuations in axial stress and bending stress due to heave ofthe vessel and roll of the vessel, respectively. For example, the pipe101 may undergo sinusoidal fluctuations in axial stress, particularlybelow the lower clamp 711, due to heave of the vessel. The lower clamp711 and the upper clamp 712 facilitate reducing or eliminating the axialstress and the bending stress in the pipe 101. As the lower clamp 711may be used to reduce or remove the axial stress load of the pipe 101,the axial stress may not be imparted to the pipe 101 supported above thelower clamp 711.

Hence, sections of the pipe 101 above the lower clamp 711 experiencereduced or eliminated axial stress due to the lower clamp 711. This mayparticularly occur in implementations in which the clamp system 710 doesnot induce axial compression into a section of the pipe 101 between theclamps 711, 712. The upper clamp 712, as shown, may then be used tosupport the pipe 101 to remove or limit the bending stress imparted intothe pipe 101 above the upper clamp 712. The section of the pipe 101between the clamps 711, 712 may experience no axial stress and onlybending stress. Limiting the axial stress of the pipe 101 mitigatesfatigue of the pipe 101 and promotes increase lifespan of the pipe 101.

Limiting the axial stress and/or bending stress of the pipe 101 alsofacilitates a wider operating envelope for the vessel having the clampsystem 710. For example, the vessel having the clamp system 710 may beused to lay pipeline in a wider range of conditions, such as in harsherweather conditions.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A clamp system for supporting a pipe on a vessel,comprising: a first clamp for coupling to the pipe; and a second clampfor coupling to the pipe, the second clamp disposed above the firstclamp; wherein at least one of the first clamp or the second clamp ismovable relative to the other of the first clamp or the second clamp. 2.The clamp system of claim 1, wherein: at least one of the first clamp orthe second clamp is movable along a longitudinal axis of the pipe toadjust a distance between the first clamp and the second clamp; and atleast one of the first clamp or the second clamp is rotatable relativeto the other of the first clamp or the second clamp in at least oneplane parallel to the axis.
 3. The clamp system of claim 2, wherein eachone of the first clamp and the second clamp is rotatable relative to theother of the first clamp and the second clamp in two planes parallel tothe axis simultaneously.
 4. The clamp system of claim 1, furthercomprising one or more actuators, each of the one or more actuatorsbeing coupled to the first clamp at a first end and coupled to thesecond clamp at a second end.
 5. The clamp system of claim 4, wherein atleast one of the first clamp or the second clamp is movable relative tothe other of the first clamp or the second clamp by actuating the one ormore actuators.
 6. The clamp system of claim 2, further comprising anoverhead structure with the second clamp translatably coupled to theoverhead structure and the first clamp rotatably coupled to the overheadstructure.
 7. The clamp system of claim 6, wherein: the second clamp istranslatably coupled to the overhead structure through a plurality ofactuators; and the first clamp is rotatably coupled to the overheadstructure through a plurality of links and a plurality of sphericalbearings.
 8. The clamp system of claim 7, further comprising one or moreactuators coupled to the plurality of links, each of the one or moreactuators being coupled to one of the plurality of links at a first endand the overhead structure at a second end.
 9. The clamp system of claim8, wherein each of the one or more actuators comprises a hydrauliccylinder.
 10. The clamp system of claim 7, further comprising a platformwith the second clamp coupled to the platform below the platform and thefirst clamp movable with respect to the platform along the longitudinalaxis of the pipe.
 11. The clamp system of claim 10, wherein the secondclamp is rotatable with respect to the platform in at least one planeparallel to the longitudinal axis of the pipe.
 12. A method ofsupporting a pipe on a vessel, comprising: coupling a first clamp to apipe, the pipe comprising a longitudinal axis; coupling a second clampto the pipe; and moving at least one of the first clamp or the secondclamp relative to the other of the first clamp or the second clamp whilethe first clamp and the second clamp are clamped to the pipe.
 13. Themethod of claim 12, wherein the moving at least one of the first clampor the second clamp comprises adjusting a distance between the firstclamp and the second clamp.
 14. The method of claim 12, wherein themoving at least one of the first clamp or the second clamp comprises:rotating at least one of the first clamp or the second clamp relative tothe other of the first clamp or the second clamp in at least one planeparallel to the longitudinal axis of the pipe while the first clamp andthe second clamp are clamped to the pipe.
 15. The method of claim 12,further comprising: applying compressive stress to a section of the pipebetween the first clamp and the second clamp.
 16. The method of claim12, wherein the moving at least one of the first clamp or the secondclamp comprises: actuating one or more actuators coupled to the firstclamp to move the first clamp relative to an overhead structure of thevessel.
 17. The method of claim 12, wherein the moving at least one ofthe first clamp or the second clamp comprises: using a line and a sheaveattached to the second clamp to move the second clamp relative to anoverhead structure of the vessel.
 18. A clamp, comprising: a pluralityof clamping layers comprising one or more lower layers and one or moreupper layers disposed above the one or more lower layers, each of theone or more lower layers comprising: one or more variable squeezecylinders, and one or more actuating clamp members; and wherein apressure within each of the one or more variable squeeze cylinders ismaintained at a constant value when the one or more actuating clampmembers are in contact with a pipe.
 19. The clamp of claim 18, whereineach of the one or more lower layers comprises one or more accumulators.20. The clamp of claim 19, wherein each of the one or more upper layerscomprises one or more actuating clamp members to contact the pipe.